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<head>
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  <title>Document</title>
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    /* 未访问过的 */
    a:link {
      color: #333;
      text-decoration: none;
    }
    /* 访问过的 */
    a:visited {
      color: sandybrown;
    }
    /* 鼠标经过 */
    a:hover {
      color: red;
    }
    /* 鼠标点击 */
    a:active {
      color: seagreen;
    }
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<body>
  <a href="#">小猪佩奇</a>
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